This invention relates to a navigation system and more particularly to a display of a location or position of another vehicle in a display unit in the navigation system.
In a satellite navigation system, a location or position of an automotive vehicle is indicated in a map picture on a display unit by means of points, signs and the like. For convenience of explanation, a typical example of a conventional navigation system will be described below by referring to FIG. 5. FIG. 5 is a schematic explanatory view of a conventional navigation system.
A terminal device 20 in a conventional navigation system, as shown in FIG. 5, comprises a GPS (Global Positioning System) receiving unit 21 which receives satellite signals transmitted from a plurality of GPS satellites 30 at an antenna 21a, a signal processing unit 22 and a display unit 23.
In this system, when the GPS receiving unit 21 receives satellite signals from the plurality GPS satellites 30, the signal processing unit 22 computes a position in coordinates on the basis of the received signals and translates the computed data of the position in coordinates into a figure such as a point, a sign, or the like to indicate the figure on the display unit 23.
Such a system is utilized in a display of position of not only in a main vehicle but also a related vehicle in the case that a plurality of vehicles are moving. If each vehicle is provided with a transmitting and receiving unit (transceiver), which communicates with a navigation terminal device in the related vehicle with respect to position data in coordinates, in addition to the same navigation system, it is possible to transmit the position data in coordinates in a main vehicle to respective related vehicles and to indicate the positions of all such vehicles on respective map pictures.
Since the location of a plurality of vehicles can be mapped, such a system is of obvious benefit when a number of vehicles are travelling together.
However, the system involves the following problems. When the display unit indicates the positions of the main and related vehicles at the same time in order to map a position between the vehicles, a map picture needs to be reduced in the case where the vehicles are separated from each other, since the position of the related vehicle is indicated on the map picture which displays the position of the main vehicle. Then, information on the map picture such as characters, map signs, and the like is reduced so that it becomes difficult to view.